Valves, especially ball valves of the aforementioned type, are generally known. They essentially comprise a housing, in which a valve ball is mounted as a blocking element. A channel that extends in the direction of gas flow within the valve ball serves as a flow guide in such valves. In an open position of the valve the input is connected to the output of the valve in the flow direction through the channel of the valve ball and they are isolated from each other in a closed position via the valve ball. In order to be able to rotate the valve ball from the open position to the closed position, the valve ball is connected to a trip shaft arranged essentially orthogonal to the flow direction to rotate the valve ball and the valve ball is rotatably mounted through two seals enclosing the valve ball. Because of the high friction caused by the two seals increased torque and therefore energy are required in order to move the ball. This makes the use of such solutions impossible or only possible with limitations in explosive-hazardous areas.
In the already known valves, which are used in the gas space and reach the open and closed position by means of a linearly movable piston, the essential drawback is that, when used as gas valves, they are opened or closed by means of a piston. In these linear solutions only a fraction of the energy is required for opening or closing in comparison with ball valves with two seals. However, a compact design of the valve is not possible here because of the stroke of the piston. At the same time higher pressure losses occur during flow of the gas than in ball valves. At high volumetric flow rates, which require greater diameter of the flow channel, such piston valves can only be used with limitations because of the large required space.
Prior art valves are already known, for example, from German Patent Application DE 42 30 341 A1, whose rotation of the valve ball from the closed position to the open position and vice versa occurs through an electromechanical drive. This rotational movement of a valve axis is transferred via a gear to a cam using a coupling connected to the ball cock. Maximum rotation of the ball cock by 90° is then admissible through the cam. In this case, two switches are required to control the motor to drive the valve axis.
A generic valve is also disclosed in U.S. Pat. No. 4,046,350, which is driven by means of a force actuator operated by an electric motor. The actuator is connected to a ball valve by means of a shaft. The shaft has gear teeth, which engage with teeth of a piston. Through longitudinal movement of the piston rotation of the shaft and therefore displacement of the ball valve by a maximum of 90° occurs. Other variants of valves are those in which a piston permits opening and closing of the channel through a linear movement. These known linear systems, however, have the drawback that they cause high pressure losses in the gas and restrict the maximum attainable flow. In addition, it is not possible or only insufficiently possible with valves of this design to continuously influence the gas flow by using intermediate positions, i.e., to operate in a modulating manner.
Another problem of the valves already known from the prior art is sealing of the ball valves. The valve ball is mounted in the housing via two bearing rings, which abut the valve ball on the front and rear in the flow direction of the fluid through the ball valve. An O-ring is provided in each bearing ring, which is supported on the outer peripheral surface of the valve ball. In order to guarantee that the O-ring ensures sealing even during slight movements of the valve ball, it is desirable that the O-ring be movable as a whole and forced against the valve ball surface by means of a spring force. This means that the present systems operate with demanding compensation mechanisms, for example, spring elements, or compensate for tolerances via high compression of the sealing elements. Because of this high power is required for movement from one position to another, which also has a particularly disadvantageous effect. The hazard of jamming of sealing elements is also high in such systems and/or long-term stability is lacking. The use of two O-rings is also not satisfactory, since high losses develop by friction at both locations.
A further drawback of gas valves known from the prior art is the fact that these gas valves are comprised primarily of metal components, which is naturally very cost-intensive. They are scarcely usable or adaptable for other systems, since an adapted solution of the valve system exists for each requirement with respect to power supply, which also leads to high development demands and also high costs during changes in specification. Simple and cost-effective assembly of the gas valves is also not present.
Another drawback of known valves relates to the fact that they are not suitable for battery operation owing to low efficiency of the motor drives. This means that the valves cannot be used directly in the gas phase or only with restriction.
Thus there is a need for a compact electric motor driven valve, which avoids the aforementioned drawbacks.